1. Field of the Invention
The present invention relates to a method and system for automating the process of conducting psychophysics experiments, including test set-up, test administration, and data analysis.
2. Description of the Related Art
Psychophysics is commonly defined as the quantitative branch of the study of perception, examining the relations between observed stimuli and responses and the reasons for those relations. Since its inception, psychophysics has been based on the assumption that the human perceptual system is a measuring instrument yielding results (experiences, judgments, responses) that may be systematically analyzed.
Because of its long history, its experimental methods, data analyses, and models of underlying perceptual and cognitive processes have reached a high level of refinement. For this reason, many techniques originally developed in psychophysics have been used to unravel problems in learning, memory, attitude measurement, and social psychology.
In the general paradigm of visual psychophysics, a human subject is presented with accurately controlled stimuli, and in certain prescribed ways, is asked what he sees. From the results of these experiments inferences can be made about the nature of visual processes.
In the printing industry visual psychophysics testing can be used wherein there is to be correlated human perceptions of print quality with physical measurements such as, for example, gray levels, halftone screening, density control, and the like. Five psychophysics testing methods which have been used in the printing and other display industries include the Paired Comparison, Ranking Order, Rating Scales, Ratio Scales and Categorical Scales methods.
The Paired Comparison method involves making pairs of all possible combinations of a group of different print samples. The sample pairs are shown to the observers who in turn select which one of each pair is of the higher visual print quality. The law of comparative judgments is applied to analyze the data. The results are shown with a table of data and graphs.
The Ranking Order method involves ranking all samples in order of quality. For example, if an observer was shown four images, the observer would be asked to rank them number 1 through 4, in order of quality. Number 1 would correspond to the best of the 4 images. Number 4 would correspond to the worst. Like the Paired Comparison method, the law of comparative judgments is applied to analyze the data.
The Categorical Scale method involves viewing each sample alone and not in comparison with others. The observer is asked to place each sample in a category which has been pre-defined by the experimenter. For example, the experimenter may set up the following image categories: (1) lowest imaginable quality, (2) low quality, (3) acceptable quality, (4) high quality, and (5) highest imaginable quality. The observer would be shown one sample at a time and instructed to place that sample in one of these five categories.
The Rating Scale method involves a comparison of a sample with two standards which are at both extremes of the quality scale. The observer is told that the one standard which is associated with the highest quality image is ranked number 10 on a 10 point scale. He is further told that the other standard which is associated with the lowest quality image is ranked 0 on the same scale. Finally, he is shown each of the samples, asked to compare each with the two standards and assign a numerical rating between 0 and 10 to each sample.
The Ratio Scale method is very similar to the Rating Scale method previously described. The only difference is that only one standard is used for purposes of comparison and assigning a numerical rating.
The above methods themselves and their statistical analysis are fully described in James Bartleson and Franc Grum,"Visual Measurements", which is Volume 5 in "Optical Radiation Measurements", Academic, Orlando, 1984; and J. P. Guilford, "Psychometric Methods," McGraw-Hill, 2.sup.nd Edition, 1954, which publications are incorporated herein by reference in their entirety.
The process of conducting a psychophysics experiment is time and labor intensive. It involves the generation of the samples to be observed, the randomization of the samples, the observation of the samples by the test subjects, the collection of the observation data, and the statistical analysis of the data. Many experiments require 15 to 20 or more observers to view the samples. Thus an experimenter's job would involve generating the samples, randomizing the samples for each of the 15-20 observers, collecting the data during each of the 15-20 observation sessions, and conducting the statistical data analysis by hand.
Because of the time and labor intensive nature of this testing, there is a need to automate the process, thereby greatly reducing the testing time.